Tree 4-17 m. Leaves membranous, oblong(-lanceolate), 10-18(-27) by 3-6.5 cm, base (rounded to short-)attenuate, apex acute-acuminate; Inflorescences with sparse woolly hairs (0.2-)0.5 mm; Fruits (in Sumatra) 2 or 3 together in a short infructescence 2-3 cm long, glabrous, ellipsoid, 2.2-2.4 by 1.5-1.6 cm, apex rounded, base contracted into a 2-4 mm long narrowed part;
Asia-Tropical: Borneo present (Sabah present, Sarawak present); Malaya (Peninsular Malaysia present); Sumatera (Sumatera present)
Malesia: Sumatra, Peninsular Malaysia, Borneo (Sarawak, Sabah).
According the structure of the male flowers, the present species is related to H. polyspherula, especially the slender specimens of var. polyspherula. Horsfieldia macilenta differs from H. polyspherula in the more slender twigs, thinly membranous leaves, and slender and tiny inflorescences.